There have so far been well-known processes for forming a color proof from a plurality of black-and-white half dot images prepared by a color-separation and a half dot image conversion in a color plate-making.printing process, such as an over-lay process in which a color image is formed by making use of a photopolymer or a diazo compound, and a surprint process.
The over-lay process has such an advantage that the operations are very simple and the production cost is inexpensive and, in addition, the process can also be utilized for proofing only by superposing four color film sheets (in the primary colors of subtractive color mixture and black). However, this process has such a disadvantage that a gloss is produced by superposing the film sheets and, therefore, the resulting texture is different than the texture of printed matter.
The surprint process involves superposing colored images on a support. This type of process includes the well-known processes described in, for example, U.S. Pat. Nos. 3,582,327, 3,607,264 and 3,620,726, in which a colored image is obtained by utilizing the stickiness of a photopolymeric materials and a toner development.
There are also the well-known processes as described in Japanese Patent Examined Publication No. 47-27441/1972 and Japanese Patent Publication Open to Public Inspection (hereinafter abbreviated to JP OPI Publication) No. 56-501217/1981, in which a color proof is prepared in the following manner. An image is formed by transferring it onto a support by making use of a light-sensitive colored sheet, by exposing it to light and then by developing it. After that, another colored sheet is laminated thereon and then the same procedures are repeated so as to prepare the color proof.
There is also a well-known process as described in JP OPI Publication No. 59-97140/1084, in which colored images are obtained by making use of a light-sensitive colored sheet and the corresponding color-separation films are each exposed to light and developed, and the resulting colored images are each transferred onto a support so that a color proof can be formed thereon. The toners for forming the above-mentioned images and the colorants for colored sheets have the advantage that the same coloring materials as printing inks can be used Therefore, the resulting color proof closely resembles the original in color tone.
However, these processes have the following disadvantages. In the steps for preparing a color proof, images have to be superposed and transferred and it takes a long time to complete the operations and, in addition, the production cost is also expensive.
As for the processes capable of eliminating the above-mentioned disadvantages, there are the processes in which a color proof can be prepared by making use of a silver salt color photographic light sensitive material comprising a white support, such as disclosed in JP OPI Publication Nos. 56-113139/1981, 56-104335/1981, 62-280746/1987, 62-280747/1987, 62-280748/1987, 62-280749/1987, 62-280750/1987 and 62-280849/1987.
In these processes, a proofing image is used in the form of a color image that is formed in the following manner. Plural color-separated black-and-white halftone dot images are prepared by converting a colored original document into plural color-separated halftone dot images. The resulting plural B&W halftone dot images are printed one after another on one sheet of color paper in a contact printing method or the like. The printed images are color developed so that a color image is formed of the dyes produced imagewise by the couplers. The resulting color image is to be used as the proofing image.
The above-mentioned technique, however, has the following defects. When the color image is adjusted to approximate the color of printed matter, the density of the black image such as the density of letters is inferior to that of the printed matter and, on the other hand, when means are taken for enhancing the density to try to approximate the density of the black image such as that of letters to the density of the printed matter, the approximation to color image of the printed matter deteriorates. Therefore, it is difficult to produce a proof image where both the color image and the black image are simultaneously a good approximation to printed images.
As for the techniques capable of improving the above-mentioned disadvantages, there have so far been the well-known techniques of adding the 4th layer that is a black printer layer having a spectral sensitivity different from any other yellow, magenta and cyan color developing layers. Besides these techniques, Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP OPI Publication) Nos. 2-289846/1990 and 2-183251/1990, and so forth also disclose the techniques for improving the above-mentioned disadvantages. However, any satisfactory effects have not been enjoyed from these techniques.
Each of the techniques mentioned above have the serious problems of the practical application that the productivity is reduced due to the increase of the numbers of exposures. Accordingly, there have been demands for further improvements.
Further, when a color image is made approximate to a printed matter by making use of a silver salt color photosensitive material, there is such a serious problem as the deterioration of image sharpness (that is a halftone dot reproducibility). When a color image is used as a color proof, the above-mentioned image sharpness, that is a halftone dot reproducibility, is one of the definitely essential qualities.
The following methods have been well-known so far as the methods for improving the image sharpness of silver salt color photosensitive materials.
(1) A method of making use of a water-soluble dye for preventing any irradiation production;
(2) Another method of increasing the filling concentration of the white pigment contained in a polyolefin layer coated on a reflection type support laminated with polyolefin on the base paper thereof;
(3) A further method of thinning a photographic component layer containing hydrophilic colloid; and
(4) Still further method of including, in a photographic component layer, a compound capable of releasing a development inhibiting compound when the layer is developed.
The above-mentioned method (1) is applied to any commonly marketed color photosensitive materials for printing use. In this method, however, the water-soluble dye content is low and the reflection densities in the wavelengths of 450 nm, 500 nm and 700 nm are each less than 0.5, before the subject color photosensitive material is developed. Therefore, any color proof having both satisfactory image sharpness and fidelity cannot be prepared.
About the method (2), JP OPI Publication Nos. 61-284763/1986, 61-27049/1986, 61-270750/1986 and so forth described thereof. Still in this method, however, any image satisfiable for a color proof cannot be prepared.
In the method (3), there is a limitation to make a photographic component layer thinner. Therefore, any satisfiable effects cannot be obtained.
In the method (4), any image satisfiable for a color proof cannot be prepared, although an edge effect may be emphasized in low spatial frequencies.